Help, Codes P1128 & P1130

[P-51 Mustang]

I have a 2001 Boxster which has been giving me ALOT of trouble since I bought it. The car has 63000 miles and has been running bad for awhile. It began to run rough at low RPM's and I thought it was a fuel system problem so I have replaced the fuel pump and fuel filter. Then the AOS went out and I continued to drive it until recently I replaced that and fixed the smoking issue. The car seemed to do fine so I put a fabspeed exhaust on it which replaced the secondary cats with resonators and put an new muffler on. Now I have the CEL with codes P1128 and P1130. The car runs terrible at RPM's lower than 1500. the idle if I give it a lot of gas off Idle it will backfire or misfire (im not sure which one) and has a very rough idle to the point the whole car shakes. I read that those codes say it is running too lean. I thought that maybe the MAF went bad from the river of oil in the intake manifold, or the plugs could be fouled out. I have new plugs but don't want to put them in until the mixture is right. Does anybody have an idea of what my problem could be? Thanks!!!!

[pomocanthus]

I had same problem around 60K. Do you have K&N air filter? In my case, I over-oiled the K&N filter and the oil droplets were released into the air flow and contaminated the MAF. A contaminated or failing MAF will give you all kinds of problems. The first thing you need to do is clean your MAF. There are many threads here showing you how. After that I recommend you give the throttle body and intake manifolds a good cleaning to remove the oil. There are threads for this too. :renntech: Note that the TB and intakes are downstream of the MAF so the oil there could not have contaminated the MAF. After a good MAF cleaning, my car ran OK for a while but I ended up replacing it. Apparently, it is common for them to die around 60K.

I also ended up replacing the upstream O2 sensors and replaced the spark plugs. Also replaced AOS. The best few hundred dollars and couple of days of work I have ever spent on the car. It looks like you already have the biggest hurdle done. The hardest DYI in this bunch is the AOS R&R. You should be able to do the rest yourself.

Good Luck,

Hung

Edited January 26, 2008 by pomocanthus

[pomocanthus]

One other note. Does the exhaust smell rich? Mine was running really rich because the MAF was giving the computer false readings and the computer thinks that it is running too lean (your 1128 and 1130 codes). It tries to enrich the mixture to the point of back firing, which I think is uncombusted fuel getting in the exhaust stream and combusting in the cats or muffler. Don't run your car too long in this condition; you might damage the cats, which is way more expensive than a new MAF, new O2 sensors, and new plugs combined.

[P-51 Mustang]

I am going to try cleaning the MAF first and checking for some leaks downstream of the MAF. Ill let you know what fixes it. Thanks for the help!

[P-51 Mustang]

so far I have cleaned the MAF and cleaned the throttle body along with throttle position indicator and it seems to be doing better. I cleared the codes and they haven't come back yet.

[Chris_in_NH]

so far I have cleaned the MAF and cleaned the throttle body along with throttle position indicator and it seems to be doing better. I cleared the codes and they haven't come back yet.

i know you've already replaced the A/OS, but if you have oil in the TB *after* changing the A/OS, it is quite possible that the *new* A/OS has failed incredibly quickly. it is certainly a possibility.

there is also a quite simple way to test your MAF to see if it causing the running problems (but not the oil in the TB). disconnect the MAF's wiring harness, but leave the MAF in place. disconnect the negative battery cable for at least a minute to reset the DME/ECU. re-connect the neg battery cable, leaving the MAF disconnected (this will not cause any harm to your car/engine). start the car. if it runs 100% better, it's the MAF. if you want to double-check it, re-connect the MAF's wiring harness and your rough running should return.

keep in mind that if you disconnect the battery, you will need the radio code to get it working again.

[tXster]

I had the same CEL codes at 66K and after driving 1100 miles in two days. AOS, MAF, O2 sensors, have been replaced. Due to rough and chasing idle, I cleaned the throttle body and recently cleaned the MAF. Car appears to be running better, no new CEL (fingers crossed) for over 1500 miles.

[germaniac]

I have a 2001 Boxster which has been giving me ALOT of trouble since I bought it. The car has 63000 miles and has been running bad for awhile. It began to run rough at low RPM's and I thought it was a fuel system problem so I have replaced the fuel pump and fuel filter. Then the AOS went out and I continued to drive it until recently I replaced that and fixed the smoking issue. The car seemed to do fine so I put a fabspeed exhaust on it which replaced the secondary cats with resonators and put an new muffler on. Now I have the CEL with codes P1128 and P1130. The car runs terrible at RPM's lower than 1500. the idle if I give it a lot of gas off Idle it will backfire or misfire (im not sure which one) and has a very rough idle to the point the whole car shakes. I read that those codes say it is running too lean. I thought that maybe the MAF went bad from the river of oil in the intake manifold, or the plugs could be fouled out. I have new plugs but don't want to put them in until the mixture is right. Does anybody have an idea of what my problem could be? Thanks!!!!

Hi, I am having the exact same problem with my Boxster and am hoping you have gotten to the bottom of it, so I can as well:)

Any news and/or luck?

Thanks in advance,

Rob

[Loren]

I have a 2001 Boxster which has been giving me ALOT of trouble since I bought it. The car has 63000 miles and has been running bad for awhile. It began to run rough at low RPM's and I thought it was a fuel system problem so I have replaced the fuel pump and fuel filter. Then the AOS went out and I continued to drive it until recently I replaced that and fixed the smoking issue. The car seemed to do fine so I put a fabspeed exhaust on it which replaced the secondary cats with resonators and put an new muffler on. Now I have the CEL with codes P1128 and P1130. The car runs terrible at RPM's lower than 1500. the idle if I give it a lot of gas off Idle it will backfire or misfire (im not sure which one) and has a very rough idle to the point the whole car shakes. I read that those codes say it is running too lean. I thought that maybe the MAF went bad from the river of oil in the intake manifold, or the plugs could be fouled out. I have new plugs but don't want to put them in until the mixture is right. Does anybody have an idea of what my problem could be? Thanks!!!!

Hi, I am having the exact same problem with my Boxster and am hoping you have gotten to the bottom of it, so I can as well:)

Any news and/or luck?

Thanks in advance,

Rob

Please do a search here - this has been covered many many many times here.